1. Field of the Invention
The present invention relates to the structure of a prober, and an electric evaluation method of semiconductor devices using the prober.
2. Description of the Background Art
A prober is a device for evaluating electric characteristics of semiconductor devices formed on a wafer by contacting input/output terminals of chips with probe needles to make signal transmissions to/from a tester.
FIG. 15 is a side view schematically showing the structure of a conventional prober. A wafer 109 with semiconductor devices to be evaluated (not shown) is placed on a chuck 108. In the upper surface of the chuck 108, an electrode 108a is provided to establish electric contact with the semiconductor devices from the back surface of the wafer 109. This electrode 108a is connected to a power supply 111 via a wire 110. Also, an electric heater 107 for controlling the temperature of the wafer 109 during evaluation of the semiconductor devices is provided in the chuck 108.
With a recent scaledown of semiconductor devices, the ability to perform an evaluation in a microcurrent region has increasingly been required of the prober. The chuck 108 is thus disposed within an electromagnetic shielding 101 to shield electromagnetic waves produced by peripheral equipment such as the power supply 111 thereby to reduce an electric noise which adversely affects evaluation.
In the electromagnetic shielding 101, a ventilation fan 102 for ventilating the electromagnetic shielding 101 is provided. Also, a loader 106 for driving the chuck 108 in each direction X, Y, Z shown in FIG. 15 is provided in the electromagnetic shielding 101. The loader 106 includes an XY loader portion 106c for driving the chuck 108 in the directions X, Y; and a Z loader portion 106d for driving the chuck 108 in the direction Z. The top end of the Z loader portion 106d is fixed to the bottom surface of the chuck 108. The loader 106 further includes a motor portion 106a for producing a driving force given to the XY loader portion 106c and the Z loader portion 106d; and a driving-force transmission portion 106b for transmitting the driving force to the XY loader portion 106c and the Z loader portion 106d.
Further on the upper surface of the electromagnetic shielding 101, a tester head 103 is placed with a probe card 104 disposed in the bottom. Part of the upper surface of the electromagnetic shielding 101 is open, through which probe needles 105 of the probe card 104 protrude into the electromagnetic shielding 101.
In this conventional prober, the electromagnetic shielding 101 can shield electromagnetic waves produced by the peripheral equipment, e.g., the power supply 111, but cannot shield electromagnetic waves produced by the equipment disposed therein, e.g., the ventilation fan 102, the motor portion 106a of the loader 106, and the electric heater 107. In the electric evaluation of semiconductor devices using such a prober, unshielded electromagnetic waves become several hundred fA levels of electric noise, interfering with the evaluation in the microcurrent region.